tf T 294 PRACTICAL ORGANIC CHEMISTRY
PREPARATION 76. ]
Phenol—Fusion of the alkali salt of the sulphonic acid i
with caustic soda or potash is a common method for preparing j
phenols (see Prep. 106, p. 219). Phenols correspond in consti- '
tution to the tertiary alcohols of the aliphatic series, but differ
in their more negative character. The phenols dissolve in j
caustic alkalis, forming alkaline phenates, which are, however, '
decomposed by carbon dioxide. In this way a phenol may be I
separated from an acid. The solution in caustic soda is satu-
rated with carbon dioxide, and the phenol is then extracted
t with ether or filtered off. The entrance of nitro-groups into
the nucleus converts phenols into strong acids (see Preps. 79
*/* • The various reactions which the phenols undergo are illus-
trated in Preps. 79—84.
The technical method for obtaining phenol is by shaking out
„ • :, with caustic soda the " middle oil" of the coal-tar distillate, after
* ' some of the naphthalene has crystallised out. The phenol dis-
solves in the alkali, and is then removed from insoluble oils.
§The alkaline liquid is acidified, the phenol separated, distilled,
and finally purified by freezing.
'. " , PREPARATION 77.
| Anisole.—The preparation of anisole from phenol is analo-
gous to Williamson's synthesis of the ethers (see p. 236), but the
ethers of phenol cannot be obtained by the action of the alcohol
on the phenol in presence of sulphuric acid. This reaction can,
however, be effected in the case of the naphthbls (see p. 316).
Another method of replacing hydrogen by methyl, in addition
to the use of alkyl halide and alkyl sulphate, is by the action of
diazomethane on the phenol :
CflIIaOII + || ;>CHa = CflH5OCH3 + No.
The methyl group in anisole can be split off, and the phenol
regenerated by heating with HC1 or HI,
CBH5OCUS + III = CIT.,I + C,,IIBOII.
The latter reaction has been made the basis of a quantitative